The field of the invention is artificial corneas and lenses, and more particularly, through-and-through keratoprostheses.
The front of the eye is covered by the cornea. The cornea refracts light through the anterior chamber and into the lens area of the eye. In the lens area of the eye, muscles control the size of the entrance aperture of the eye, also known as the pupil. The lens is suspended in this area and focuses the refracted light through the vitreous chamber and onto the retina in the back of the eye. The shape of the lens can be varied by muscles within the eye to focus on objects that are close or far away.
Often, irregularity in vision is created by problems with the cornea and/or the lens. In addition, many people have severe corneal disorders caused by accidents. For example, millions of people are unable to see due to severe dry eye conditions, alkali explosions, traumatic lacerations, or other accidents wherein acid or some other such chemical has come into contact with the surface of the eye. Such accidents usually produce permanent opacity in the cornea and lens of the eye. Some patients having occular chemical burns may receive corneal transplant surgery using donor human corneal material to replace the scarred, opaque cornea. In the overwhelming majority of the chemical burn cases, however, this is not possible due to the shortage of such donor material, rejection by the recipient's body and most importantly, the presence of an abnormal ocular surface and dry eye syndrome which usually remains after ocular surface burns; the last two of which reduce the chances of successful corneal transplantation to less than 1 in 5.
In order to solve this problem, the medical community has attempted to develop a variety of artificial devices which may be used in place of a corneal transplant. One such device is known as a keratoprosthesis. There are essentially two types of keratoprostheses; the "nut and bolt" keratoprosthesis and the "through-and-through" keratoprosthesis.
The nut and bolt keratoprosthesis involves surgically implanting a cylinder into the eye and using a nut made from some synthetic material and positioned on the back side of the cornea to secure the cylinder. The cylinder then acts as both the lens and the cornea to focus light onto the retina. While using a similar optical cylinder, the concept of the through-and-through keratoprosthesis involves surgically implanting a base plate within the cornea to support the optical cylinder.
While the idea behind a keratoprothesis has existed for a long time, the major problem has been in making a successful keratoprosthesis out of a biocompatible material. The major reasons for failure of presently used keratoprostheses are related to the bioincompatibility of the materials which produce wound leaks, ocular infections and extrusion of the keratoprosthesis from the eye.